1. Field of the Invention
The invention relates generally to a method for enhancing the germination of seed and, more specifically, to a method of treating seeds with sound waves to accelerate the rate of germination and improve the percentage of total germination.
2. Background of the Prior Art
Modern agricultural practices have improved the productivity of farmland many fold. One of the principal advances that has led to this improvement is the development of improved lines and varieties of agronomically significant plants, particularly hybrid corn varieties. The development of a plant breeding program for improving corn under went an explosive expansion in the last century. Historically, corn was grown as open-pollinated varieties having heterogeneous genotypes. The farmer selected uniform ears from the yield of these genotypes and reserved them for planting the next season. The result was a field of corn plants in which segregation was reduced, i.e., were homozygous, for a variety of traits. This type of selection led to at most incremental increases in seed yield and tended to accumulate deleterious genes.
Large increases in seed yield were the result of the development of hybrid corn varieties in plant breeding programs. The ultimate objective of the commercial corn industry is to produce high yielding, agronomically sound plants, which perform well in certain regions or areas suitable for the production of corn, particularly the United States Corn Belt. Hybrid varieties are not uniformly adapted for all locations, or even for the entire Corn Belt, but are specifically adapted for separate and identifiable regions that have particular soil types, climatic conditions, and other environmental characteristics which affect the selection of corn hybrid varieties for planting and growing. For example, northern regions of the Corn Belt require hybrids with times to maturation that are shorter than those of hybrids that prosper in southern regions of the Corn Belt.
Seed companies, therefore, target hybrid seed corn varieties for different geographical regions. One of the characteristics of corn lines and varieties identified and tracked by corn breeders is the length of time in days of the growth period of hybrid varieties. The growth period in this case is the average length, in days, between the time the cotyledon of the seed of a hybrid variety emerges from the soil and the time the grain produced on the plant is mature and dry enough for harvest. Hybrid varieties with shorter growth periods are generally more suitable for planting in northern geographical regions or areas of higher elevation where temperatures remain colder later in the spring and drop earlier in the fall. The success of the development of specialized hybrid varieties for specific growing seasons is exemplified by the fact that some seed companies break the United States into as many as eleven regions based upon growing seasons varying from 70 to 118 days. In general, a farmer will plant hybrid varieties which have the longest growth period for the area in which the farmer's fields are located. This is because hybrids with longer growth periods will typically yield higher than hybrids with shorter growth periods. The differences in growing seasons targeted by seed companies are only a matter of a few days. Accordingly, shortening the time period between planting and maturity may have significant commercial benefits to farmers and may allow for the cultivation of corn or other crops in new agricultural areas previously unsuitable for crop production.
Corn researchers monitor and select for corn lines which have good germination traits, measuring the germination of seed under cold soil conditions as well under ideal warm, moist conditions. Corn seed typically will not germinate in soil temperatures below 40.degree. F. While the total percentage of seeds that germinate improves as temperatures increase, farmers currently wait until soil temperatures are 50.degree. F. or higher before planting to assure a high percentage of total germination within a reasonably short time period.
Another aspect of seed germination of importance to the seed industry is that germination, particularly germination at colder temperatures, declines with the age of seed. Accordingly, commercial seed corn which has germination characteristics that are commercially acceptable within the first several years following production, may no longer be commercially acceptable after having been warehoused for, say, four or five years. Currently, seed companies will discount such seed and sell it in regions that have warmer spring soil conditions where the percentage total germination will still be commercially acceptable at the discounted price.
The decline of germination with age is also of great concern to seed depositories which accept and maintain, or attempt to maintain, in a viable state, seeds of diverse and perhaps rare species and varieties. While these seed deposits are maintained under carefully controlled conditions which greatly extend the length of time the seed remain viable, the seed depositories must nonetheless periodically grow plants from deposited seed in order to produce fresh seed. Any method which would enhance the percentage of seeds which germinate after being stored for extended periods of time would not only decrease the cost of maintaining viable deposits of seed, but may also mean the difference between survival or extinction of rare species or varieties which are difficult to store and maintain.
Finally, the period of time a seed sits in the soil prior to germination can also affect yield. Ungerminated seeds are prone to bacterial and fungal damage, and may be prone to damage or dislocation due to environmental conditions most notably temperature change and precipitation. A reduction in the period of time to germination i.e., the time between planting and emergence of coleoptile and root from the seed could have a significant impact both on the percent of germination, the heartiness of the plant facilitated by a head-start, and yield.
Seed priming has been attempted in the past through the use of environmentally unsafe chemicals such as polyethylene glycol and concentrated salt solutions. None of these known methods, however, have been found to significantly accelerate the germination of seeds or improve the total germination percentage without adversely affecting the plant produced from the treated seed.